1. Field of the Invention
The invention in general relates to electrical switches, and more particularly to one which is used in a cryogenic environment to accomplish both electrical and thermal disconnects.
2. Description of the Prior Art
Various electrical systems or components require operation at cryogenic temperatures. For example, in electromagnetic launcher apparatus, hundreds of thousands to millions of amperes are provided to a parallel rail arrangement for propelling a projectile along the rails to a desired velocity. One common type of power supply to deliver these currents utilizes a homopolar generator which charges an inductor to a certain firing level whereupon the current stored in the inductor is commutated into the rails.
In order to be able to accommodate megamp currents, the inductor is quite massive and is operated at cryogenic temperatures to significantly reduce the resistance of the inductor coils so as to increase the inductance-to-resistance ratio.
With the inductor connected in circuit during non-operating conditions, thermal heat leaks through the electrical connections require a continual replacement of the cryogenic coolant which is utilized. Accordingly, a need exists for a connect/disconnect switch capable of carrying megamp currents during operation of the inductor while providing thermal isolation when the inductor is disconnected from the remainder of the apparatus.